Field of the Invention
The invention relates to a tailored semifinished part in the form of a metal sheet or strip which is formed from a first plate and at least one second plate and the first and at least one second plate are physically, frictionally and/or adhesively joined to one another, where the first plate consists of an ultrahigh-strength, monolithic material, and also a motor vehicle component made of the tailored semifinished part of the invention.
Description of Related Art
Tailored semifinished parts are known from the prior art and are referred to in the art as “tailored blanks” or “tailored welded blanks” for metal sheets and as “tailored strips” or “tailored welded coils” for strip-like, in particular rolled-up, rolls/coils. They have the advantage that they can be processed further to give components, in particular motor vehicle components, which compared to monolithic materials have properties which can be individually configured according to need. For example, at least two materials of the same type having different sheet thicknesses or else materials of different types can be joined to one another.
Examples of tailored semifinished parts and also structural components produced therefrom for motor vehicles are disclosed under the link: http://www.i-car.com/pdf/advantage/online/2004/120604.pdf. Furthermore, a process for producing a component for a motor vehicle is known from the European patent document 2 228 459. The semifinished part disclosed, which consists of a blank composed of a hardenable steel material and a blank composed of a high-manganese steel material which are joined to one another by means of a laser welded seam, is heated to an austenitization temperature of the hardenable steel material and shaped in a hot forming tool and at the same time cooled in such a way that a martensitic microstructure is formed in the hardened steel material. Thus, different properties can be set in the component. The hardened region has high tensile strengths at a relatively low elongation at break, while the region formed by the high-manganese steel material has no significant property loss even after the heat treatment, viz, the high elongation at break is retained at a moderate tensile strength. In the case of components which are stressed in a crash in automobile construction, in particular, at least two different regions which can be divided into at least one strong/hard region which in the case of a crash prevents intrusion and protects the passenger cell and at least one soft/ductile region which absorbs crash energy by deformation are advantageous. However, soft/ductile materials which have a high elongation at break have limited tensile strength. In addition, not all materials are suitable for hot forming without their properties, in particular in respect of the elongation at break, being impaired as a consequence of hardening. The trend in automobile construction is to reduce the vehicle weight in order to reduce the emission of CO2. This can be achieved by, firstly, replacement of materials with, for example, lighter materials, which in the case of some components is not possible or possible only with great difficulty and, associated therewith, generally also only at greater cost, or, secondly, by a further reduction in the thickness of existing components, in which case the necessary increase in the strength of the material comes up against technical limits.